The syndrome associated with the human genetic disease von Recklinghausen neurofibromatosis (NF) has a number of features which suggest that some of the neural crest-derived cells in these patients have become unstable in their phenotype. Some of the glial cells of peripheral nerves divide uncontrollably and undergo a metaplastic transformation into melanocytes. In previous work, we found that the phorbol ester TPA induces similar changes in crest-derived cells of early avian embryos. Some of the glial cells of the dorsal root ganglia (DRG) of quail embryos, exhibit abnormal growth characteristics and transform into melanocytes when cultured in the presence of TPA. We wish to determine the extent to which TPA treatment of embryonic avian cells mimics other features of the NF syndrome in patients. Since NF-associated tumors are almost exclusively associated with neural crest and neuroectodermal derivatives, we will first test whether the TPA-induced metaplasia of embryonic avian cells shows a similar embryological specificity. This will involve treating various quail tissues with TPA in culture, grafting them into host chicken embryos, and then comparing the range of derivatives to which they give rise. A second feature of human NF is the progression of some NF-associated benign tumors to a malignant state. We will determine whether treatment with TPA (possibly in conjunction with a carcinogen) in culture will cause these embryonic avian cells to develop into either benign or malignant NF-like tumors when grafted into host embryos. Since a third feature of human NF is the changes in severity of symptoms at puberty or with pregnancy, we will test whether various hormones and/or peptide growth factors can influence the TPA-induced metaplastic transformation of avian DRG cells. In addition, we will test whether TPA induces a similar transformation in mammalian DRG cells, and will perform experiments to determine whether TPA exerts these effects on avian embryonic cells via stimulation of protein kinase C, as has been shown in a number of other systems. This proposal is designed to examine the possibility that phrobol esters might bring about cellular changes in avian embryonic cells which mimic the pathophysiological changes resulting from the NF mutation, and therefore would serve as a model system for this disease.